At many locations at which there is a swimming pool it is important that the physically handicapped have an opportunity to use the pool. However, getting the physically handicapped into and out of the pool can be troublesome. A pool can be constructed with a wheel chair ramp but, for one reason or another, many are not. Ramps are not necessarily the ideal solution even when the problem is anticipated at the time that the pool is constructed.
Platforms (elevators) which move vertically in the pool have been proposed as a solution to this problem. However, the power means for moving the platform vertically have not been entirely satisfactory. One form of a power means has been chains or cables which are actuated by a winch or a hydraulic cylinder, etc., located outside the pool. This has the advantage that the oil employed in and around the winch, hydraulic cylinder, etc., will not contaminate the pool. For the same reason the chain or cables and any of the pulleys therefor which are in or above the pool cannot be lubricated. In addition to that minor disadvantage, there is a major disadvantage from the standpoint of safety. It is very difficult to arrange chains or cables in a manner such that they are not accessible to mischievous children who can be injured by grasping them while the platform is moving, etc. Such systems suffer from a further disadvantage that they require a great deal of maintenance and attendant expense.
Another form of power means has been some form of hydraulic cylinder directly attached to the platform to raise and lower the platform. Since it is nearly impossible to prevent a hydraulic cylinder from leaking, the usual hydraulic fluids must be avoided since they are oily and will contaminate the water in the pool. Also, the use of hydraulic cylinders can result in complications due to uneven loads on the platforms. It is not practical to anticipate that the platform will be uniformly loaded. Thus the apparatus should be capable of accepting unequal load, e.g., more on one side than on the other. While a single ram can stand a limited amount of non-uniform loading, the more there is the larger must be the ram and the greater is the wear and tear on the ram bearings, etc. Even when using a multiplicity of rams, an unequal loading can cause the ram closest to the heavy loading to act as a pump supplying hydraulic fluid to the lightly loaded side, thus just increasing the effect of the unequal loading.
The present invention relates to a simplified apparatus for supplying the force to raise and lower a platform in a swimming pool. It has the advantages that: it is dependable; it does not become inordinately expensive; it can be easily adapted to lifts installed in new or existing pools of almost any shape; and it will have an excellent service life, even under conditions of unequal loading of the platform. An important feature of the invention is that water is used in the hydraulic system of the cylinders which do the actual raising and lowering of the platform. Thus there is no contamination of the pool due to leakage. A simple arrangement is provided to keep this hydraulic system filled with water by always adding the required amount of make-up water. Further objects and advantages will become apparent from the following description.